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Output third order intermodulation intercept point

After activating the OIP3 measuring mode the tinySA asks first for the first test signal frequency and then for the second test signal frequency. The tinySA then configures itself with a span of five times the difference in frequency and the center at the average of the two frequencies. The specified frequencies do not have to be exact but within 20%. In the image below the left test signal was specified at 8MHz but it happened to be at 7.8MHz

As the phase noise of the tinySA is not very good it is important to use two test signals that are preferably at least one MHz apart

Two normal tracking markers are enabled that will be position on the two strongest signals. Marker 1 at the left signal, marker 2 at the right signal. Two delta markers are also enabled and these are automatically positioned at the calculated 3rd order intermodulation products. As can be seen in below image the regular information for markers 1 and 2 is shown but the information for markers 3 and 4 is replaced by the calculated OIP3 levels. Two numbers are given, one calculated from the left intermodulation product, the second calculated from the right intermodulation product.

The attenuator setting is extremely important. With low attenuation it is very well possible the tinySA first mixer performance is limiting the maximum OIP3 that can be measured. Changing the amount of attenuation should note change the measured OIP3. If it does you should increase the attenuation until it no longer does.

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Page last modified on May 13, 2020, at 12:17 PM